The present invention relates to a data transfer apparatus having a safety circuit for safe operation of drive means for data storage media such as CD-ROMs, that is, compact disks used as read-only memories.
The CD-ROM drive disclosed in the U.S. Pat. No. 5,844,866 represents an example of data transfer apparatus. The CD-ROM drive lends itself to use as an external storage of a personal computer. The CD-ROM for use with a personal computer has a tray built into it, for accommodating a CD-ROM (hereinafter to be also referred to simply as disk). In small-size CD-ROM drives for small-size personal computers such as those of the notebook size, an optical pickup for reading data on the disk, a disk drive motor for imparting rotation to the disk, and a feed motor or sled motor for feedling the optical pickup radially of the disk are all mounted to the tray, which is movable between a first position, in which it protrudes from the housing of the personal computer, and a second position in which it lies within the housing.
When the tray is in the first position, for loading or unloading the disk on or from the disk drive motor, the disk-mounting portion of the disk drive motor and the objective lens of the optical pickup are both exposed. Therefore, should the disk drive motor, and hence the disk itself, be left in rotation when the tray is pulled out of the computer housing, they might do harm to the user or operator. This hazard is avoided by incorporating in the CD-ROM drive a tray position sensor for ascertaining whether or not the tray is in the second position with respect to the computer housing. The disk is driven only when the sensor detects tray insertion into the computer housing.
The CD-ROM drive includes a microcomputer, or a controller including a central processor unit, for controlling the rotation of the disk drive motor. If the eject button is operated, or an eject command is supplied from the master, when the disk drive motor is in rotation under the direction of the controller, the controller will respond by setting the disk drive motor out of rotation before causing the eject means to eject the tray. The eject means when so actuated will cause the tray to protrude slightly from the housing, permitting the user to manually pull the tray to the first position for a change from one disk to another.
Thus, as long as the controller is functioning normally, the disk drive motor and the disk will go of rotation before the tray is pulled out. There will therefore be no danger to the operator.
The CD-ROM drive is additionally equipped with emergency eject means for compulsorily ejecting the tray when the latter is not normally ejectable by the eject means. The emergency eject means is such that an emergency hole is formed in the front panel of the CD-ROM drive for insertion of a pin thereby to unlock the means locking the tray in the second position. Trying to emergency eject the tray when the CD-ROM drive is electrically powered on, the operator will be subject to no danger as long as the controller is functioning properly. That is because upon compulsory tray ejection, the tray sensor will put out a signal indicative of that fact, to which the controller will respond by terminating the rotation of the disk drive motor, thereby assuring the safety of the operator.
Although not frequently, however, the controller may malfunction and endanger the operator. The disk drive motor may then be left in rotation after actuation of the eject button or emergency ejection. The motor will then revolve on the ejected tray, potentially doing harm to the operator.
Another possible trouble is that the controller, either itself malfunctioning or under the influence of external noise, may deliver a drive command to the disk drive motor while the tray is ejected. Then the motor will start rotation, driving the ejected disk at the risk of injury to the operator.
It should also be taken in consideration that the laser and the pickup feed motor are also under the control of the controller. The emission of the laser beam is automatically terminated, and the feed motor set out of rotation, upon tray ejection. The malfunctioning controller may keep the laser beam emitted, and the feed motor running, with the tray ejected. The operator may suffer injury from these causes, too.
The foregoing problems of the CD-ROM drive also exist with the digital video disk (DVD) drive, the DVD-ROM drive, the magnetic disk drive, and so forth.
It is therefore an this invention to provide a data transfer apparatus enhanced safety.
The data transfer apparatus according to the invention comprises drive means for driving a replaceable data storage medium, support means supporting said drive means, a cover covering said drive means and the data storage medium mounted to said drive means, positioning means for selectively positioning said support in a first position, where said drive means is exposed from said cover so as to permit the data storage medium to be mounted to and dismounted from said drive means, and a second position where said drive means is covered by said cover, a position sensor for sensing whether said support is in said second position or not, drive command generator means for generating a command for driving said drive means, control means connected to said drive means and said position sensor and said drive command generator means for setting said drive means in operation when said position sensor provides a signal indicating that said support is in said second position and, at the same time, when said drive command generator means generates the drive command for said drive means, and for setting said drive means out of operation when said position sensor provides a signal indicating that said support is not in said second position, and safety circuit means connected to said control means and said drive means and said position sensor for providing to said drive means a signal for stopping said drive means regardless of an output from said control means when said position sensor provides a signal indicating that said support is not in said second position.
Data storage media envisaged by this invention are those media which permit data to be written on and/or read therefrom, examples being those in disk form such as optical disks, magneto-optical disks, and magnetic disks, as well as those in tape form.
If, in the data transfer apparatus according to the present invention, the output from the control means indicates the operation of the drive means when the position sensor indicates that the support is not in the second position, the safety circuit means will compulsorily set the drive means out of operation, overriding the output from the control means. Operator safety is thus assured as the drive means is compulsorily prevented from operation when the drive means is uncovered.
Preferably, the position sensor included in the data transfer apparatus according to the present invention should include a switch that assumes a first state (on or off) when said support is in said second position, and a second state (off or on) when said support is not in said second position. It is also desirable that the position sensor should put out a signal of a first potential (low or high) when said switch is in the fist state, and of a second potential (high or low) when said switch is in the second state.
The safety circuit means of the improved data transfer apparatus according to the present invention may be constituted of a pnp transistor. The safety circuit means can thus be most simplified in construction.
Another improved data transfer apparatus according to the present invention has a resistor connected between the output of the position sensor and the input of the control means. The resistor assures positive operation of the safety circuit means even if the input of the control means has a low potential because of some trouble.
As an additional feature of the present invention, the drive means for the storage medium may be fixedly mounted to the computer housing, and the cover may be made movable relative to the housing.